Dispersion powders have been used for many years specifically in the building sector as polymer improvers of hydraulic setting systems. Substantial improvements in the properties of adhesion, abrasion resistance, scratch resistance and flexural strength are achieved by the addition thereof. In many cases, for example, in concrete repair, the increase in adhesive strength is the reason for using the dispersion powder.
Dispersion powders are produced by spray drying of aqueous polymer dispersions with the addition of polyvinyl alcohol and other additives. The free-flowing powder having particle sizes between 10 and 250 .mu.m redisperses in water to again give the original dispersion having particle sizes between 0.1 and 5.0 .mu.m. The redispersions should also be stable over a relatively long period of time, i.e. they should not tend to settle.